Composite material of metal and plastic

ABSTRACT

A composite material is produced from a metal core and fiber-reinforced plastic material, in which the reinforcing fibers penetrate into and entwine around the metal core without coming into contact with the metal core. Parts for aircraft and turbine construction can be made from the composite material to provide higher impact strength and rigidity at less weight as compared to metal components.

FIELD OF THE INVENTION

This invention relates to a composite material composed of a metal andplastic material in which a metal substrate is embedded in the plasticmaterial and is provided with apertures forming passageways.

PRIOR ART

Composite materials with a textile-fiber and textile-cord substrate orcore and a matrix of thermoplastic or thermosetting materials have beendisclosed in DE-OS No. 28 51 526. Such composite materials havedisadvantages that they do not satisfy the requirements of dimensionalstability, rigidity and notch strength for aircraft and turbineconstruction, for example, for tail assemblies and engine components.

Such disadvantages are exhibited also by composite materials having aplastic matrix and a lattice or mesh type reinforcement formed, forexample by wires, as disclosed in DE-OS No. 15 59 464. This arrangementis further deficient due to differences in thermal expansion between themetal mesh and the plastic matrix, which under extreme thermal loads,such as on aircraft tail assemblies and engine components, may destroythe composite material.

SUMMARY OF THE INVENTION

In a broad aspect of the present invention, therefore, a composite ofmetal and plastic materials is provided in which, on the one hand,temperature effects are substantially prevented from being transmittedthrough the generally thermally conductive metal and, on the other hand,the composite can be given greater fracture and impact strength than thenon-metallic material would possess alone.

In accordance with the invention, a composite material is formed from aflat metal substrate provided with a plurality of apertures distributedtherein embedded in a body of synthetic resin material, all with aplurality of reinforcing fibers wound through the apertures withoutcoming substantially into contact with the substrate.

The invention enables expensive metallic raw materials to be economized,and despite the greater strength and rigidity in comparison with thesemetals and the composite materials disclosed in DE-OS No. 28 51 526 andDE-OS No. 15 59 464, an approximate weight saving of up to 30% isachieved over metallic raw materials, depending on the compositecomponent.

This invention permits the metal substrate to be ideally embedded in thefiber-reinforced plastic with a bond that exceeds mere cementing. Themetal substrate can be made very thin, i.e. less than 1 mm, to economizematerial. Layers of graphite, carbon, aromatic polyamide or glass fibercan be built into layers 0.05 to 0.2 mm thick.

This invention creates a number of novel potential applications for sucha composite material, which in this domain is counted among the group ofhybrids. An essential advantage provided by such material is its lowweight, its good processability and the high quality of its finish.Parts of such composite material can be simply and cheaply manufacturedin bulk. The composite finds advantageous uses in engine and airframeconstruction, i.e. in the aerospace industry. It finds applications alsoin stationary plants and in vehicles. It can be used in the manufactureof complete tail assemblies, fuselages, wing skins, shells, flaps,fairings, radomes, casings, intermediate and outer casings, and thelike.

By constructing the composite material from a metal core and afiber-reinforced plastic, where the metal core is multiply joined to theplastic without establishing contact between the metal core and thereinforcing fiber, one great advantage is obtained that the strongerconstituent, especially when it is the metallic material, has superiorelongation and still absorbs energy when the reinforcing fibers,filaments, or similar means, like those disclosed in DE-OS No. 28 51526, have already broken--a situation that can readily occur under highmechanical loads, such as impact load. For this purpose, the metallicmaterial has apertures to form passageways, such as bores, holes, pores,ducts or other cavities, through which the reinforcing fibers in theform of filaments, fibers or whiskers can singly or in groups of two ormore be linked together to form fabrics, nets, mats, felts or laminates.In the process, the reinforcing fibers pass through the openings orcavities in the metal core, or are guided, pulled or forced throughthem, optionally by a mechanical method such as employed in a sewingmachine, where the individual reinforcing fibers are advantageouslyfirst impregnated with plastic or the cavities of the metal core arefirst infiltrated therewith, while the plastic material is still in aplastic condition. In this manner, the thermal expansion and the modulusof elasticity of the metal core are adapted to suit those of thereinforcing fibers and of the plastic matrix penetrating and surroundingthe metal core.

The plastic material can be a synthetic resin and thermoplasticmaterials can be used to great advantage, because they bond well withthe metal core and readily penetrate into the passageways in the metalcore. The reinforcing fibers can be inserted, pulled or pressed intoposition as long as the thermoplastic has not rehardened. Use can bemade also of durometer materials, such as ABS or other thermosettingsynthetic resins.

For the metal core, this is advantageously made of materials selectedfrom the group including steel, superalloys, titanium, aluminum, copper,metals from the platinum group (sub-group VIII of the Periodic Table)and alloys containing at least one of these metals.

According to an advantageous aspect of the present invention, ametal-plastic fiber precomposite consisting of a plastic-infiltratedmetal core and plastic-impregnated reinforcing fibers of non-metallicfilaments, fibers, whiskers, or fabrics, nets or similar structures madetherefrom, is manufactured in a first step, after which a sandwich-typelaminate or a semifinished or nearly finished end product or thefinished part is manufactured. For this type of molding in plasticmaterial, various spraying, casting or pressing processes, particularlycold or hot pressing, are employed as they are commonly practiced in theplastics industry.

Various intermediate steps, especially pre- and post-treatment, can beused as desired to suit the starting materials or the desired finalcondition. An injection compound containing carbon, for example, can bedecarbonized, or a base part or a substrate can be siliconized ornitrided. Similarly, a base part or substrate already containing carboncan at least partially be converted into a carbide, and elements thatcan be made to react in a hydrogenous atmosphere, can be treated in ahydrogenous atmosphere during deposition by reactive sputtering, dustingor ion bombardment.

A special advantage is afforded also when in a pretreatment process forthe plastic material, particulate substances such as metal particles inthe form, for example, of powder, flakes or whiskers, are admixed withthe plastic, because this will produce a more favorable, or more gradualtransition or the coefficient of thermal expansion from the metal coreto the fiber-reinforced plastic material.

In another advantageous aspect of the present invention, the surface canfinally be improved by enameling, glazing or metallizing. The compositematerial can be metallized in various ways known from the manufacture ofsubstrates for printed circuit boards used in the electronic circuitry.Also dispersion or doping of particles of foreign materials in surfacesby high-energy beams is a conventional practice that can be used.Advantageously, the plastic materials permit cross-linking and/or curingin a mould.

Embodiments of the present invention are described more fully withreference to the accompanying drawings, where they are shownschematically.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING

FIG. 1 illustrates a metal substrate or core of a composite material.

FIG. 2 is a sectional view on enlarged scale which illustrates the metalcore joined to a reinforcing fiber.

FIG. 3 is a plan view of a fiber structure showing warp and weft threadsthereof.

FIG. 4 is a sectional view which illustrates a laminated compositematerial of sandwich construction having a metal core.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference now to FIG. 1, therein is seen a metal core or substrate1 of a composite product which will be referred to as a compositematerial and is generally indicated in FIG. 4 by numeral 4. The core 1is substantially flat and can be a metallic panel, layer, sheet orsimilar structure of small thickness, especially in a sheet gage in themillimeter range and less. The core 1 is provided with openings 2incorporated in the metal by electroplating, through-cladding, etching,drilling, eroding or similar process. The openings 2 are arranged in adesired size in a uniform or irregular spacing over the surface of themetal core 1. An important consideration in this context is that theopenings 2 should be larger than the reinforcing fibers to passtherethrough, but not very much so, just enough so that plasticimpregnation or infiltration creates a spacing between the metal core 1and the reinforcing fibers 3 so that contact of the reinforcing fibers 3with the metal core is prevented, especially in areas where thereinforcing fibers 3 pass through the openings 2.

The number and distribution of the openings 2 in the metal core isselected such that the mechanical strength of the metallic portion as awhole is not greatly reduced. The metal core 1 can be manufactured byrolling, for example, metal sheet or otherwise especially as a tape,produced by film-deposition techniques using vapor-deposition,electroplating or chemical deposition processes. In the process aremovable plastic substrate can temporarily be joined to the metal core,or vice versa. The openings or apertures 2 in the metal core 1 can beround bores, round holes, pores or the like, and the reinforcing fibersare a material such as an aromatic polyamide, carbon or glass, or ahybrid combining two or more of these materials.

FIG. 2 illustrates a reinforcing fiber 3 passing through one of theopenings 2 in the metal core 1. To prevent direct contact of thereinforcing fibers 3 with the metal core 1, the reinforcing fibers arelinked together singly or in groups of two or more after having beenimpregnated or coated, e.g. by dipping, and/or chemically treated withsynthetic resin, such as epoxy resin or polyimides.

Alternatively, the metal core 1 in the form of a sheet, laminate, foamor the like, is soaked with the above-mentioned plastic materials, i.e.it is infiltrated, especially its openings, again by dipping or similarmethod, to make sure that the reinforcing fibers 3 can pass through theopenings 2 without coming into contact with the metal because theplastic keeps them separated.

FIG. 3 illustrates an advantageous arrangement of the reinforcing fiber3 as a fiber structure, where the reinforcing fiber 3 is first joined tothe metal core 1 by a weaving or winding technique, namely by formingwarp and weft threads wound through the openings 2 to produce a fabricor similar netting interwoven in the metal core 1 and at least partiallysurrounding the core to form a metal-plastic fiber composite.

FIG. 4 illustrates the composite material in a laminated sandwich formbrought to its final shape from the metal-plastic fiber precomposite byspraying, pressing, casting or otherwise coating it to form asemifinished product or laminate. In the process the metal core 1 canproject from the composite at one or both sides. In FIG. 4 the core 1projects from one side. When using a plastic material, such as athermoplastic material, a spraying or casting process is recommended forsynthetic resins such as polyethylene, and a pressing process forpolyimides. A thermal hardening cycle, a cross-linking cycle and/or acuring cycle can be used as an intermediate or post-treatment,especially with an additional dispersion process for particulate matter.

The laminated sandwich shapes or composite materials of multiplyvertically alternating construction or optionally with a protrudingmetal core 1 for anchorage, may be made in the form of endlesssemifinished products to be cut to length, for example, a tape,especially when they are made by injection molding or pressing methods,or they may be in the near-net shape of a component requiring but asmall amount of finishing, or they may come as a finished product (i.e.with final dimensions).

The invention has been described in relation to specific embodimentsthereof. However, it will become obvious to those skilled in the artthat numerous modifications and variations can be made within the scopeand spirit of the invention as defined in the attached claims.

What is claimed is:
 1. A composite material comprising a flat metalsubstrate provided with a plurality of apertures distributed therein, abody of plastic material in which said flat metal substrate is embeddedand a plurality of reinforcing fibers on said substrate and woundthrough said apertures, said reinforcing fibers being embedded with saidsubstrate in said plastic material and being substantially out ofcontact with said substrate.
 2. A composite material as claimed in claim1 wherein said flat metal substrate is a foil or laminate.
 3. Acomposite material as claimed in claim 2 wherein said fibers are carbon,glass or aromatic polyamide.
 4. A composite material as claimed in claim3 wherein said plastic material is a thermoplastic or a durometermaterial.
 5. A composite material as claimed in claim 1 wherein saidmetal substrate is a metal selected from the group consisting oftitanium, aluminum, copper, an element from Group VIII of the PeriodicTable, or alloys thereof.
 6. A composite material as claimed in claim 1wherein said fibers comprise individual filaments.
 7. A compositematerial as claimed in claim 1 wherein said fibers are wound as afabric, fleece, felt, mat, web or mesh.
 8. A composite material asclaimed in claim 1 wherein said apertures are round holes.
 9. Acomposite material as claimed in claim 1 wherein said metal substrateprotrudes from said body of plastic material.
 10. A composite materialas claimed in claim 9 wherein said metal substrate where it protrudesfrom said body of plastic material is devoid of said reinforcing fibers.